Circuit for electric discharge devices



March 30, 1948. HEHENKAMP 2,438,556

CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed Feb. 17, 1943 0 MUCH.0.0.0.000.

Invenkor: Theodorus Hehenkamp,

His ATTOTIWEBQI Patented Mar. 30, 1948 CIRCUIT FOR ELECTRIC DISCHARGEDEVICES Theodorus Hehenkamp, Eindhoven, Netherlands, assignor, by mesneassignments, to General Electric Company, Schenectady, N. Y., acorporation of New York Application February 17, 1943, Serial No.476,215 In the Netherlands April 6, 1940 Section 1, Public Law 690,August 8, 1946 Patent expires April 6, 19.60

3 Claims.

My invention relates to circuits for electric discharge devices, andmore particularly to circuits for devices employing filamentaryelectrodes such as fluorescent lamps.

It is known to connect the series-connection of a serially-connectedcondenser and a choke coil to a source of alternating current, and tobridge the condenser by the series-connection of another choke coil anda gas-discharge tube, the first-mentioned choke coil, which may also bedivided, for example into two portions, and the condenser being sodimensioned that between the terminals of the condenser there is set upa high voltage which ignites the discharge tube.

This device has very satisfactory properties not only as regards theignition but also the operation of the discharge tube. Thus, forexample, it is possible to obtain with this device a very satisfactorypower factor which may be even substantially equal to unity.Furthermore, it is easy to obtain the advantage that the higherharmonics produced by the discharge tube can penetrate to the source ofcurrent only to a slight extent and that the device is slightlysensitive to the voltage variations occurring in sources of current.

One drawback of this prior art device resides, however, in that upon theclosure of the switch with the aid of which the device is connected,

to the source of current a high voltage is set up across the terminalsof the condenser and in other parts of the device even when thedischarge tube is not in its holder or holders. At the same time a heavycurrent passes in this case through the condenser and through the chokecoil connected in series therewith. In this case there exists the dangerthat when one forgets to open the said switch again this high voltageand this heavy current remain in existence, which not only implies anunnecessary loss of energy but also may lead to deterioration of thedevice.

A further drawback of the known circuit arrangement is seen in that ifthe discharge tube comprises incandescent electrodes, and if it isdesired to heat the latter prior to the ignition of the discharge tube,it is necessary to take particular steps, which complicate the device.

In devices wherein all the auxiliary elements required for the ignitionand the operation of the gas-discharge tube are connected in series,these drawbacks may be avoided by incorporating the incandescentelectrodes or a conductive bridge provided in the cap or caps of thdischarge tube in this series connection so that tilting state.

only the discharge path of the discharge tube is located in parallelwith a portion of the seriesconnection. The properties of these devicesdiffer, however, from those of the first-mentioned device wherein theseries connection of a choke coil and a discharge tube is located inparallel with a condenser which in turn is connected in series withanother choke coil.

It is, however, impossibledirectly to modify the last-mentioned devicein such manner that all the auxiliary elements are connected in seriessince in this circuit-arrangement there is a particular point ofjunction, viz. a point which is connected not only through a choke coilto the discharge tube but also through two branch circuits to the twoterminals 01 the source of current.

A circuit arrangement of this kind which comprises such a point ofjunction connected through a choke coil to the tube, will hereinafter beshortly referred to as junction-point system.

Such a junction point also occurs in other devices comprisinggas-discharge tubes. It is known, for example, to connect a gasdischarge tube in series with a choke coil to a source of alternatingcurrent and to mount in parallel with the tube plus the choke coil acondenser which has for its purpose to reduce the phase lag of thecurrent taken from the source of current or even to convert it into alead. Here again arises the drawback that when a voltage is applied tothe device while the discharge tube is not present in the latter, acurrent flows through the condenser, which means a useless load on thesource of current with a greatly leading current. Besides, also in thisdevice the incandescent electrodes which the discharge tube may comprisecannot be heated prior to the ignition without taking particular steps.

A further case wherein such a junction point is present occurs with adevice wherein a condenser and a choke coil are connected in series withon another to a source of current and the series-connection of agas-discharge tube and a choke coil is located in parallel with thefirstmentioned choke coil, this choke coil and the condenser being sodimensioned that with the non-ignited discharge tube, due to thesaturation of the choke coil which occurs in this case, a very heavycurrent flows through the circuit and consequently there prevailsbetween the ends of this choke coil a high voltage which ignites thedischarge tube whilst after the ignition oi the discharge tube the saidcircuit leaves the If a voltage is applied to this dedifferentintensities.

vice while the discharge tube is not present a heavy current flowspermanently through the condenser and the choke coil due towhich theycan easily be deteriorated. Furthermore, in this device heating of theelectrodes prior to the. ignition of the discharge is impossiblewithoutfurther steps.

The invention has for its object to obviate the;

above-mentioned drawbacksof such devices in which there is a similarpointof. junction and to retain at the same time the .electricproperties, of these devices.

The device according to the invention corresponds t known junction-pointsystems in-thatit comprises a discharge tube which is provided iliaryelectrodes) and eac'h'of whichcomprises' two current supply members(AandB, C and D.

respectively) whilst the .membersAis connected" through a choke coiland,v as the case'may'be, through another impedance to a terminal of asource of alternating current? and." the member C is'connected, as thecase-may be, through an impedance to the second-terminal ofv this sourceof. current.

According; to the presentinvention; the choke coil comprises anauxiliary winding and the memberBis connected throughthisauxiliarywinding and'an'i impedance to the member D, the. auxil-"- iary windingbeing wound in such manner that" upon the passage of a series-currentthrough the main winding and the auxiliary winding of. the? chokecoilmagnetic fields are generated which counteract one another.

' stituted thereby. The choke coil 9' mayalso In this device all theauxiliary elementsand both-conductive bridges present in or on thedischarge tube are connected in series so:that,.

when--thedischarge tube is removed from the: holders, the circuit isnecessarily interrupted. If th'esaid bridges constitute the incandescentelec-- trodes or the heating elements of the (indirectly heated)incandescent electrodes, these 'elec'- trodesor-their heating elementsare directlypresent in the series-connection formed and 'they' areheated prior to the ignition of the discharge.

In this way we obtain the advantages of theseries-connection of theauxiliary elements; 'at the same time, however, owing to the use of the.auxiliary winding provided in a particular manner on the choke coil weobtain properties which are.

abse'ntin the hitherto knownldevices comprising auxiliary elementsconnected'in series and which correspond to the properties ofjunction-point systems. detail in the description of the form. ofconstruction given by wayof example.

'Thechoke coil may be, at least partly, bifilarly wound. During normaloperation there pass through the two windings in general currents of Dueto the fact that bifilar winding with Wires of difierent. thicknessesrequires an excessive winding space, it may be advantageous toconstitute the. windings by stranded wire of which a determined numberofconcluctors are incorporated in the main winding and the remainder inthe auxiliary Winding.

' gas-discharge tubes are meant hereinafter This Willhereinafter beexplainedfim one or more gases but also tubes which contain a fillingofvapour or Qf a..mixtur,e of gas and vapour. I

The invention will be explained more fully with reference to theaccompanying drawing which represents diagrammatically,by way ofexample; one embodiment thereof.

In the drawing, l denotes a discharge tube serving for the radiation. oflight, which is constituted bya tubeihaving, for example, a length of100' cms. and a diameter of 3.5 cms. and which .comprisesitwo thermionicelectrodes 2 and 3 provided with a substance of highelectron-emissivity; The lamp contains a filling of rare gas, for

exam-pleargon, at a pressure of a few mms. of mercury and, inaddition, asmall quantity of mercury which exhibits during operation a lowpressuremercury vapour discharge with a positive column. The inner surface ofthe wall of the tube may be coatedzwith a luminescent substance which isexcited to; luminescence by-i'the ultra-violet rays:generated vin: thedischarge: ,It: is, of. course, also possible'to'rutilize-in the devicedischargestubes: of.

according to the invention other type.- V

Each of; the-incandescent electrodes-2 and 3' is providedwithtwoncurrent supply; membersv 4, 5.-and 6, 'l'respectively whichcorrespond to' the above-mentioned members AD.". The member iof :theelectrode 2 iscOnnected. through a choke coil winding 8 and; achokecoil-fi to the terminal lilo-f a sourceof alternating'currentwhilst; the

member f the; electrode -3-is. connected through:

theintermediary of, a. switch: H to-theother terminal lzofthe said.sourceof current. It thesource of current is constituted bya leakagetransformer or by a-g enerator having a .high self inductive reactance,the choke coil 9 may be subconsist of two. portions ofwhich the-onemaybe incorporated. in the circuit arrangement at the point'shown and the;other between the switch I l and the members- The current supplymember=5 of theelectrode. 21is connected through .a windin iafland arcon.denser M to the member 1 of the electrode-=3...

The winding l3 constitutes the auxiliary windingof the choke coilo-fwhich 8 isthe :principal V The auxiliary windingll has been wound insuch manner thatprior tothe estab winding.

lishment of adischargebetween the electrodes 2 and3the. windings 8 and13 counteract oneanother.. I 7

With the interposition of the heating elements of theincandescentelectrodes and-3the in- I d-uctive elements 9, .8 andl3'andthe capacitative element I4; are. connected-in .series with oneanother and are so dimensioned that between the electrodes there occursa'voltage which is sufficient for, the ignition of thetube; Owing to thefact that the current flowing through this ci-rcult-arrangement raisesthe electrodes; prior=to the. ignition, to .the temperatureeof emission,the

required ignition voltages; acquires a lowervaluethan is the casewithelectrodes. v

After the switch. I [has :been .closed, the maga tube comprising coldnetic fields generatedbythe windingstand I3 counteract one another sothat in the casewherein they have been chosen so as to be mutually equalthe voltage suppliedto the tube, I; is -sub-= stantially equal to thevoltage across the condenser M and, as it were,.ashort-circuitingconnection is producedbetween the points l5 311C113.

a -g h L w or the wine ings 8 and I3 is, however, not necessary asexperiments have shown.

After the tube I has been ignited, neither the intensity nor the phaseof the current passing through the winding I3 are in general equal tothose of the current flowing through the winding 8. It has been foundthat there need not exist any appreciable potential diiTerence betweenthe points I5 and I6. Thus we obtain a device which has, so to speak,interconnected points I5 and I6 and, instead of the windings 8 and I3, asingle choke coil with all the concomitant good qualities in operation.

By providing the auxiliary winding I3 it is consequently possible togive the device, wherein all the auxiliary elements are connected inseries, the properties of a junction-point system without thepossibility of giving up pre-heating of the electrode and interruptionof the seriescircuit upon the removal of the discharge tube from itsholders.

It has been found by testing that it is not absolutely necessary to formthe winding I3 in such manner and to couple it with the winding 8 sotightly that even when the discharge tube is operating there existsbetween the points l5 and I6 substantially no potential difference atall. Also in the case of a less tight coupling of the windings I3 and 8,in which event a potential diflerence of a few tens of volts was set up,between the points I5 and I6, it proved to be possible to obtain, atleast to a large extent, the properties of the junction-point system.

In one concrete case the elements of the device had been so chosen thatat a mains voltage of 220 volts and 50 cycles prior to the ignition ofthe tube the joint current passing through all the elements amounted to0.4 amp., whilst the voltage across each electrode was 12 volts and thevoltage between the electrodes was 350 volts; With the tube in operationthe current taken from the mains was 0.14 amp., the current flowingthrough the condenser was 0.225 amp. and the discharge current was 0.25amp.

The two-wire choke coil 8, I 3 was provided with an iron core having anair gap with a cross-sectional area of 3.7 sq. cms. and a length of 0.04cm. The winding I 3 consisted of 1460 turns of copper having a diameterof 0.28 mm. and the winding 8 consisted of 1360 turns with a thicknessof 0.2 mm. The winding I3 was arranged around the winding 8. In spite ofthe fact that the total current passes through the winding 8 it waspossible to take for the latter a thinner wire than for the winding I3.

With the tube in operation there occurred across the elements of thedevice the following voltages: 77 volts across the choke coil 9, 146volts across the winding 8, 2 volts across each of the incandescentelectrodes, 149 volts across the winding I3, 198 volts across thecondenser I 4 and 103 volts between the electrodes. The potentialdifference between the points I5 and I 6 was in this case 9 volts andthe power factor of the device was 0.94 lagging.

Owing to the tight coupling between the windings the potentialdifierence between the points I5 and I5 is slight. It has been found,however, that with a less tight coupling with which the winding 8 and I3were arranged side by side and there existed between them a leakagefield of such intensity that the voltage between the points I5 and I 6increased to 57 volts no appreciable change in the operation of thedevice occurred.

The application of the invention is, of course,

last-mentioned choke coil may also be so dimensioned that, prior to theignition of the tube, it is tilted over, in co-operation with thecondenser which has been substituted for the element 9, into a state ofhigh current intensity but leaves this tilting state when thetube isoperating.

The invention may furthermore also be advantageously utilized in orderto avoid more than one junction-point, Such is the case, for example,when between the member 6 and the switch I I there is achoke coil whichcorresponds to the choke coil 8 and which is provided in this case withan auxiliary winding which is connected between the member I and thecondenser I4.

In the form of construction described by way of example, the conductivebridges incorporated in the series-connection of the auxiliary elementsare formed by the electrodes 2 and 3. The discharge tube may also beprovided with two main electrodes, in which event an auxiliary electrodeis provided in the neighborhood of each main electrode. The mainelectrodes are connected in this case to the current supply members 4and 6 respectively whilst the auxiilary electrodes are brought intoconnection with the current supply members 5 and 1 respectively. Whenthe device is put into operation, auxiliary discharges are establishedbetween each main electrode and the neighbouring auxiliary electrode.These auxiliary discharges, by which the main electrodes are heated, arein series with the auxiliary elements and form the'conductive bridgesabove referred to. Here again the circuit is always interrupted when thedischarge tube is not in its holders.

The invention may also be applied when the discharge tube comprises twoelectrodes which are not heated prior to the ignition of the discharge.In this case the conductive bridges between the members 4 and 5, and 6and 'I respectively may consist, for example, of two conductors presentin the caps of the discharge tube.

What I claim is:

1. In combination, an alternating current supply circuit, an electricdischarge device of the type employing an ionizable medium and includinga pair of filamentary electrodes each having a pair of terminals, meanscomprising an inductive choke having a main winding connected in serieswith one terminal of said source and one terminal of one of saidelectrodes and an inductively coupled auxiliary winding connected to theother terminal of said electrode, means for connecting the auxiliarywinding to a terminal of the other electrode, and means for connectingthe other terminal of said other electrode to said supply circuit, saidmain and auxiliary windings being wound in such manner that upon thepassage of series current therethrough opposing magnetic fields areproduced.

2. In combination, an alternating current supply circuit, an electricdischarge device of the type employing an ionizable medium and includinga pair of filamentary electrodes each having a pair of terminals, meanscomprising an inductive choke having a main winding connected in serieswith one terminal of said source and one terminal of one of saidelectrodes and an inductively coupled auxiliary winding connected to theother terminal of said one electrode, a capacitor commentedv i-nseriesrelationawith said: auxiliary winding-angliconnectedto arrtermi alOfrthe other electrode; and means for connecting the other terminator:saidotherelectrode to said pply circu t, isaid ma n: and: -;au aryrwindin s being wound to produc counteracting magnetic fields uponthepassage ofr series current; therethrough.

' 3; In combinati0n,,;an{alternatingcurrent supply circuit, an elecylfic clischarge device of the type employing {an ionizable'medium and.including a pair of filamentary electrodes each having a pair of;temn-i-nals,,means comprising an inductive choke having; amain windingconnected in series with one terminator said. source and one terminal ofone ofjsaid electrodesand an inductively coupled auxiliary-windingconnected to the other terminalyof saidpne; electrode, a capacitorconnect-ed in series relation with said auxiliary Winding-and-connected-;tozaterminal of. the other electrode, and means forconnecting the other,

REFERENCES omen The following references are of-record. in the file ofthis patent: V

FOREIGN PATENTS Country Date Number v Australia June 10, 1942

